Visual perception of faces is a major component of the "online" processing of social information required for successful interaction with other individuals. Research from cognitive, clinical, and neuroscience approaches suggests that elements of the visual system may be specialized for processing human faces. Of particular interest is the dissociation of face processing from other categories of object processing, and from other components of visual processing, such as motion, attention, and spatial perception. Neuroimaging techniques have the potential to reveal aspects of the underlying architecture and function of visual processing. By combining data from functional magnetic resonance imaging (fMRI), magneto- and electroencephalography (MEG/EEG), and diffusion tensor imaging (DTI), we will be able to better understand the pathophysiology of three neurodevelopmental disorders: autism, Williams syndrome and developmental prosopagnosia. We will explore the dissociations observed in these three groups in order to better understand the fundamental architecture of the parts of the visual system involved with social cognition. Autistic disorder (ASD) and Williams syndrome (WS) seemingly offer complementary patterns of impaired and spared visual function. ASD individuals are poor at social interactions, at facial expression recognition but can perform well on spatial tasks, such as block design. WS individuals are hyper social, perform at age-appropriate levels on the Benton face recognition task, but are severely impaired at block construction and other spatial tasks. Another group of patients, developmental prosopagnosics (DP), are severely impaired in face recognition but are otherwise normal in all other cognitive and social domains. Our research goal will be to characterize the neural system underlying the visual-spatial and communicative aspects of face and object recognition in these three subject populations. We will examine the behavioral profile of ASD, WS and DP, and characterize their cognitive phenotypes in the domain of face processing. We will also analyze the visual cortex organization, at low (retinotopy), and intermediate (hierarchical attention) levels using fMRI, and at high levels (facial and emotional processing), in spatial and temporal domains using MEG and fMRI. Finally, we will examine the architecture of the visual stream subserving facial perception (including the amygdala) using Diffusion Tensor Imaging, Diffusion Spectrum Imaging, and cortical thickness analysis. These aims taken together should provide insight into the relation between behavioral performance and structural/functional characteristics. It should give us additional insight into the pathophysiology face perception disorders, and provide a basis for the development of remedial treatment for deficits in social communication.